Safety joint with shear pin release means



June 17, 1958 B. P. ARTERBURY ETAL 2,839,315

SAFETY JOINT WITH s EAR PIN RELEASE MEANS Filed Dec. 50, 1954 Bryanf P, Arzerbury M. C/ar/k v ATTORNEY United States PatentO SAFETY JOINT WITH SHEAR PIN RELEASE MEANS Bryant P. Arterbury and George M. Clark, Houston, Tex., assignors of thirty-three and one-third percent to Roy L. Arterbury, Houston, Tex.

Application December 30, 1954, Serial No. 478,729

1 Claim. (Cl. 2853) This invention relates generally to a safety joint as for well bore pipe or drill strings, fishing strings or the like,

and is more particularly concerned with a releasable or safety joint which may be locked in engaged or made-up position but with loose thread engagement between sections so that the sections may be quickly disengaged when unlocked, such safety joint being so constructed that fluid may be freely circulated down the string in both locked and unlocked position and may positively indicate at the top of the well when unlocking is effected.

For a number of years the trade, as the oil well drilling profession, has had need for such a tool as often when the lower part of the pipe string as a connected object below a safety joint in a pipe string becomes lodged or stuck, it is advantageous to circulate fluid freely down the string in an attempt to dislodge the lodged element. After the safety joint is unlocked prior to disconnection between the two parts of the string it may often still be advantageous to continue circulation until the safety joint has been broken and the sections thereof have been completely disengaged to effect severance between the drill string thereabove and the elements therebelow.

Consequently this invention has as a primary object the provision of a safety joint which locks the pipe string thereabove and the element therebelow against relative rotation in make-up direction while in normal operation and which is easily unlocked to permit relative rotation in direction opposite make-up to permit disengagement of the sections thereof to sever the pipe string.

It is also an object of this invention to provide a safety joint of this class through which fluid may be circulated both when in locked and when in unlocked position and which is so operative that a positive indication is rendered at the top of the well to indicate the disarming for unlocking and the unlocking of the safety joint.

It is a further object of this invention to provide a safety joint of this class which may be unlocked for relative rotation between sections by the exertion of an axially directed force on the latching sleeve thereof which disarms the sleeve to permit unlocking of the sections.

It is also another object of this invention to provide a safety joint of this class which avoids tight make-up between the sections and marring of the locking sleeve head while permitting easy disconnection of the sections when they are unlocked.

Other and further objects will be apparent when the specification is considered in connection with the drawings in which: r

Fig. 1 is a sectional elevation of the tool in locked position;

Fig. 2 is a sectional elevation of the tool in unlocked position; and

Fig. 3 is a sectional plan view taken along line 33 of Fig. 2.

Referring in particular to the drawings, a pipe string 10, as an oil well drill string or fishing string, is shown having a safety joint 11 connected thereinto, with an element 12 connected to the lower end of the pipe string 2,839,315 Patented June 17, 1958 10. The element 12 may be the lower portion of the drill string, or it may be the lower element of a fishing string which may be connected to a fish or to any object or structure which it may be desired to remove from the well bore.

The safety joint 11 includes an upper section 14 and a lower section 15 threadedly connected thereto at 16. The threads are preferably constructed to provide a relatively loosely interthreaded fit by the provision of abutting axially extending surfaces or clutch faces 17 of lugs 18, 18' on the lower and upper sections respectively. Such lugs 18, 18' are so spaced with relation to the point of full thread interengagement of the threads 16 as to abut in make-up prior to full tight thread engagement whereby the threads 16 comparatively loosely interfiti The upper section 14 has a lower end 19 which provides an enlarged inner opening 20 thereinto of noncircular cross-section, shown in Fig. 3 as of hexagonal cross-section, and in full thread engagement the lower end of the upper section may abut an inwardly extending part 21 of the lower section 15 which has an enlarged inner opening 22 of the same cross-section as the upper section lower end 19.

The thread engagement 16 between sections 14, 15 is such that when the surfaces 17 are in abutment the inner faces of the part 21 mate in co-planar co-extension with the inner faces of the upper section lower end 19. This is assured by the abutment of the lug 18, lb which thus prevents the sections 14, 15 in makeup from marring the hexagonal head 33. Below the part 21 the lower section 15 provides an enlarged inner diameter part 23 with open or passageway space 24 outwardly of the hexagonal cross-section space size of the openings 22, 20 thereabove.

Below the part 23 the lower section is of decreased inner diameter to provide a shoulder 25.

A sleeve 26 is provided to latch the upper section 14 and lower section 15 against relative rotation in direction opposite the direction of makeup rotation, the direction of makeup rotation being conventionally the clockwise direction as viewed from the top of the well. i

In assembly the safety joint 11 may be threadedly, engaged at 27 to the upper part of the pipe string 10 and with the sleeve 26 in the normal position shown in Fig. 1 a shear pin 28 is inserted in mating semi-cylindrical openings 29, 29 in the lower section 15 and sleeve 26, respectively, to thereby latch the sleeve 26 and lower section together.

The sleeve 26 has a cylindrical top 30 which bears in a bore 31 in the upper section 14, such bore being of cross-section to be at least circumscribed by the area of the opening 20. Peripherally the top 30 supports an O-ring 32 to seal the bore 31. Below the top or upper end 30 of the sleeve 26 a hexagonal cross-sectional part 33 is provided to slidably fit within the openings 20, 22 of the lower end 19 and part 21, respectively. Bearing thus in the openings 20, 22 the sleeve 26 prevents relative rotation between the sections 14, 15 while the head or part 33 remains latched in the position of Fig. 1 by the shear pin 28. For a purpose to be explained hereinbelow the part or head 33 has laterally extending ports 34 therein, or a corresponding passage means to communicate with the head periphery.

With the safety joint sleeve 26 thus assembled to the upper string the lower part of the drill string or element 12 may be assembled to the lower safety joint section 15, by threaded engagement at 35. Then the assembly is lowered through the well bore to conduct the drilling operation or a fishing operation as the case may be. In a drill string the safety joint serves as a means for saving all of the upper drill string section in case the lower element 12 may become lost or stuck in the well bore. In a fishing operation the safety joint serves as a 3 means of saving all of the upper fishing string section above the safety joint in case it may be found impossible to elevate a fish or stuck element.

Assuming a condition wherein it becomes necessary to effect disconnection within the safety joint so that the upper pipe string thereabove may be withdrawn from the well bore, it is obvious that any axially directed force which will shear the pin 23 will disarm the latched sleeve 26 so that unlocking may be effected. Such a force may be a substantial weight impacting the top 30 of the sleeve.

As best indicated in Pig. 2, a ball 36, shown in dotted lines, may be dropped from the top of the well bore to seat upon the sleeve top 3% and close the sleeve bore. Then when a fluid is circulated down the drill string 10 from the top of the well bore, a sufiicient pressure can be built up as the ball as seals the sleeve bore and as the O-ring 32 seals the bore 311, to exert ample pressure or axially directed downwardly acting force on the sleeve 26 to shear the pin 28 and force the sleeve head 33 to slide downwardly to clear the parts 19 and 21, of hexagonal internal cross-section. The head 33, as shown in Fig. 2, thus seats on the shoulder 25 and rests entirely within the enlargement 2 The upper safety joint sec tion 14 may now be rotated with the upper drill string section and relative to the lower safety joint section 15 when the direction of rotation is opposite the direction of makeup, or conventionally counter-clockwise as viewed from the top of the well bore.

While thefluid is being pumped down against the ball 36 and sleeve top 30 before the pin 28 is sheared, the fluid pressure indicated at the top of the well increases its reading. Then when the pin 28 is first sheared, the reading does not fall off until the hexagonal part of the sleeve head 33 begins to pass below the part 21 of hexagonal cross section. At this instance the pressure reading falls and remains lower than the initial pressure reading since fluid may now circulate downwardly through the annular passage 24 and through the ports 34 and the bore of the sleeve 26 and downwardly through the element 12 to the well bore. It thus results that the falling off of indicated pressure at the top of the well gives a positive indication of the shearing of the pin and the seating of the sleeve head 33 on the shoulder 25 and fluid circulation may be continued, as to hold down the upward movement of well bore pressure fluid for the time preceding disengagement of the safety joint.

When disengagement is effected, as by conventional clockwise rotation, the upper pipe string section together with the upper safety joint section 14- may be withdrawn, while the sleeve 26 and lower safety joint section 15 remain with the element 12 in the well bore.

ment which will permit circulation between the elements above and below the safety joint in both locked and unlocked position while providing a positive indication of the unlocking of the safety joint. The invention is thereby not limited by the details of disclosure set forth, but includes other forms as well. which may fall within the broad spirit thereof, and Within the broad scope of interpretation claimed and merited by the appended claim.

What is claimed is:

A tubular safety joint threadably connectable into a well bore pipe string and including threadedly connected upper and lower sections respectively having lower and upper end portions having transversely non-circular and longitudinally co-planar inner surfaces, an enlarged chamber within said lower section below said upper end portion terminating downwardly in a stop shoulder, a reduced diameter bore in said lower section extending below said stop shoulder, a sleeve having a bore therethrough of lesser diameter than the inner diameter of said pipe string and a transversely non-circular head part slidably engaging said surfaces simultaneously, frangible means to latch said sleeve in said position, means sealing said sleeve in said upper section, said head having lateral port means through its wall below the top thereof and being of a lesser length from the top thereof to the bottom thereof than the length of said chamber whereby means may be dropped. through said string to close said sleeve bore and pressure may be exerted thereon to sever said frangible means and said sleeve may be forced downwardly by said pressure fluid from above to seat the bottom of said head on said stop shoulder, said downwardly acting pressure fluid being directed into said chamber after the top of said head passes below the bottom of said upper end portion, and thence through said port means into said sleeve and down said sleeve.

References Cited in the file of this patent UNITED STATES PATENTS 1,607,096 Mueller Nov. 16, 1926 1,883,071 Stone Oct. 18, 1932 2,039,943 Wickersham May 5, 1936 2,071,375 Allen Feb. 23, 1937 2,502,886 Ragan Apr. 4, 1950 2,532,686 Ware Dec. 5, 1950 2,586,015 Edwards Feb. 19, 1952 

